Apparatus and method for driving 2-phase SRM

ABSTRACT

Disclosed is an apparatus and method for driving a 2-phase SRM capable of individually performing an initial driving by an initializing sensor and a normal driving by a driving sensor, and capable of controlling a rotation speed of the SRM by delaying a phase signal by a half period and then generating a pulse width modulation signal based on the period. The apparatus comprises: a driving sensor which detects a position of a rotor thus to generate a driving sensor signal based on a result of the detection; a microprocessor which generates a 1-phase signal and a 2-phase signal based on a rising time and a falling time of the driving sensor signal at the time of a normal driving; an oscillator which generates first and second pulse width modulation signals delayed by a preset time; and a multiplying unit which multiplies the 1-phase and 2-phase signals with the first and second pulse width modulation signals, and generates 1-phase and 2-phase driving signals based on a result of the multiplication.

TECHNICAL FIELD

The present invention relates to a 2-phase SRM (switched reluctance motor), and more particularly, to an apparatus and method for driving a 2-phase SRM by individually using an initializing sensor for an initial driving and a driving sensor for a normal driving.

BACKGROUND ART

In the conventional method for driving a 2-phase SRM, two position sensors are used to detect each position of a rotor, and generated sensor signals serve to initialize and drive each phase.

FIG. 1 is a view schematically showing a construction for detecting a sensor signal of a 2-phase SRM.

As shown, the 2-phase SRM comprises a 4-pole stator 10, a 2-phase rotor 11, a rotor shaft 12 connected to the center of the rotor 11 for transmitting a rotary motion of the rotor, a 2-phase shutter 13 rotatably connected to the rotor shaft 12, 1-phase and 2-phase sensors 14 a and 14 b for detecting a position of the shutter 13, and a sensor signal generator 15 for generating 1-phase and 2-phase sensor signals from signals detected by the 1-phase and 2-phase sensors 14 a and 14 b.

Each phase of the shutter 13 has an angle of 120°, and the two phases form an angle of 60° therebetween.

The 1-phase and 2-phase sensors 14 a and 14 b form an angle of 90° therebetween, and are positioned on the shutter 13.

In the conventional method for driving an SRM, when the shutter 13 is rotated as the rotor 11 is rotated, the sensors 14 a and 14 b detect each position of each phase of the shutter 13. Then, the sensors 14 a and 14 b transmit the detected position to the sensor signal generator 15 thus to enable 1-phase and 2-phase sensor signals to be generated.

That is, the 1-phase and 2-phase sensors respectively detect each position of each phase of the rotor, and then a microprocessor (not shown) generates 1-phase and 2-phase signals corresponding to the sensor signals. Accordingly, a current is supplied to each winding of each phase of the SRM thus to generate a torque.

FIGS. 2 to 5 show sensor signals according to each position of a rotor of the 2-phase SRM in accordance with the conventional art.

As shown, when the rotor 11 is counterclockwise rotated, the shutter 13 connected to the rotor shaft 12 starts to be rotated. The 1-phase and 2-phase sensors 14 a and 14 b detect a position of the shutter 13 thus to detect a position of the rotor 11. Accordingly, the sensor signal generator 15 generates a sensor signal of each phase.

Referring to FIGS. 2 to 5, when the rotor 11 is aligned, the shutter 13 is positioned at an angle of 0°.

FIG. 2 shows a high 1-phase sensor signal S1 and a high 2-phase sensor signal S2 when the shutter 13 is positioned within a range of 0°˜30°.

FIG. 3 shows a high 1-phase sensor signal S1 and a low 2-phase sensor signal S2 when the shutter 13 is positioned within a range of 30°˜90°.

FIG. 4 shows a high 1-phase sensor signal S1 and a high 2-phase sensor signal S2 when the shutter 13 is positioned within a range of 90°˜120°.

FIG. 5 shows a low 1-phase sensor signal S1 and a high 2-phase sensor signal S2 when the shutter 13 is positioned within a range of 120°˜180°.

A microprocessor (not shown) generates each sensor signal of each phase and modulates each pulse width of the generated signals, thereby driving the SRM.

FIG. 6 is a curve showing an SRM driving torque in accordance with the conventional art.

As shown, a 1-phase signal having a dwell time of 0°˜120° and 180°˜360° of one cycle of 360°, and a 2-phase signal having a delay of 90° from the 1-phase signal are modulated from the first and second sensor signals shown in FIGS. 2A to 2D thus to be inputted to each winding of the 2-phase SRM. Accordingly, a torque is generated as indicated by the curve of FIG. 3.

However, the conventional art has the following problems. Since the 1-phase sensor initializes and normally-drives a 1-phase and the 2-phase sensor initializes and normally-drives a 2-phase, a sufficient amount of currents are not supplied to each winding of each phase of the SRM at the time of an initial torque occurrence in a normal driving mode (e.g., t1, t2 and t3 of FIG. 3). Accordingly, a torque is not sufficiently generated thus not to normally drive the SRM.

That is, when the 2-phase SRM is driven at a high speed, each phase signal has to be risen at a point prior to an initial point so as to generate a sufficient amount of torque. However, in the conventional art, the 1-phase sensor and the 2-phase sensor detect sensor signals at the same position in an initial driving mode and a normal driving mode, thereby generating each phase signal and a signal for driving the SRM. Accordingly, a sufficient amount of torque is not generated at the time of driving the SRM at a high speed.

Furthermore, a dwell time and a rising delay time of a pulse width modulation signal are controlled based on a phase signal in order to control a rotation speed of the SRM. However, when the SRM is driven at a high speed, the phase signal has a short period and thus the microprocessor has a limited operation speed. Accordingly, it is difficult to control the dwell time and the rising delay time of the pulse width modulation signal based on the phase signal having a short period.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide an apparatus and method for driving a 2-phase SRM capable of individually performing an initial driving by an initializing sensor and a normal driving by a driving sensor, and capable of controlling a rotation speed of the SRM by delaying a phase signal by a half period and then generating a pulse width modulation signal based on the period.

To achieve these objects, there is provided an apparatus for driving a 2-phase SRM (switched reluctance motor), comprising: an initializing sensor which detects each position of each phase of a 2-phase SRM, and generates an initializing sensor signal based on the detected result; a driving sensor which detects each position of each phase of the 2-phase SRM, and generates a driving sensor signal based on the detected result; and a microprocessor which initially drives the 2-phase SRM based on the initializing sensor signal at the time of an initial driving, and normally drives the 2-phase SRM based on the driving sensor signal at the time of a normal driving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration view schematically showing a 2-phase SRM for detecting each sensor signal;

FIGS. 2 to 5 are views showing sensor signals according to each position of a rotor of the 2-phase SRM;

FIG. 6 is a curve showing a torque according to a driving method for the 2-phase SRM in accordance with the conventional art;

FIG. 7 is a block diagram showing a configuration of an apparatus for driving a 2-phase SRM according to the present invention;

FIG. 8 is a waveform showing each portion of the apparatus for driving a 2-phase SRM at the time of an initial driving according to the present invention;

FIG. 9 is a waveform showing each portion of the apparatus for driving a 2-phase SRM at the time of a normal driving according to the present invention; and

FIG. 10 is a flowchart showing a method for driving a 2-phase SRM according to the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

FIG. 7 is a block diagram showing a configuration of an apparatus for driving a 2-phase SRM according to the present invention.

As shown, the apparatus for driving a 2-phase SRM according to the present invention comprises an initializing sensor 71 a, a driving sensor 71 b, a microprocessor 72, an oscillator 73 and a multiplying unit 74.

The initializing sensor 71 a detects a position of a rotor of the 2-phase SRM at the time of an initial driving, and outputs an initializing sensor signal based on the detected result.

The driving sensor 71 b detects a position of a rotor of the 2-phase SRM at the time of a normal driving, and outputs a driving sensor signal based on the detected result.

The microprocessor 72 generates 1-phase and 2-phase signals from the initializing sensor signal and the driving sensor signal outputted from the initializing sensor 71 a and the driving sensor 71 b.

When the 2-phase SRM has an rpm more than a preset rpm after being initially driven, the microprocessor 72 normally drives the 2-phase SRM.

The microprocessor 72 generates 1-phase and 2-phase signals based on the initializing sensor signal at the time of an initial driving, and generates 1-phase and 2-phase signals based on the driving sensor signal at the time of a normal driving.

The 2-phase signal has a phase different of 90° from the 1-phase signal.

The oscillator 73 generates pulse width modulation signals from the 1-phase and 2-phase signals generated from the microprocessor 72. Also, the multiplying unit 74 multiplies the 1-phase and 2-phase signals with the pulse width modulation signals, thereby generating signals for driving the SRM (an initializing signal and a driving signal).

The initializing sensor 71 a is positioned so that the initializing sensor signals can be dwelled between a mis-aligned position and an aligned position of the 1-phase or 2-phase inductance profile.

The driving sensor 71 b is positioned so that the driving sensor signal can be risen before the mis-aligned position of the 1-phase or 2-phase inductance profile.

Preferably, the driving sensor is positioned so that the driving sensor signal can be risen before the initializing sensor signal by 10°˜30°.

The oscillator 73 generates a single pulse width modulation signal at the time of an initial driving, and generates first and second pulse width modulation signals at the time of a normal driving.

At the time of a normal mode of the SRM, each dwell time of the first and second pulse width modulation signals can be varied according to a driving speed of the SRM, and can be risen after being delayed by a preset delay time.

The oscillator 73 generates a first pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal, and generates a second pulse width modulation signal delayed by a preset time based on a rising time of the driving sensor signal.

Preferably, the preset time corresponds to a half period of the driving sensor signal.

The multiplying unit 74 may be implemented at the microprocessor 72 in a software manner or in a hardware manner.

FIG. 8 is a waveform showing each portion of the apparatus for driving a 2-phase SRM at the time of an initial driving according to the present invention.

As shown, the initializing sensor is positioned on the shutter so that the initializing sensor signal can have a dwell time between a mis-aligned position and an aligned position of the 1-phase inductance profile so as to generate a maximum initializing torque.

The microprocessor generates a 1-phase signal based on the initializing sensor signal, generates a 2-phase signal having a phase difference of 90° from the 1-phase signal, and generates pulse width modulation (PWM) signals based on the 1-phase signal or the 2-phase signal.

The 1-phase signal, the 2-phase signal, and the pulse width modulation signal are multiplied with one another, thereby generating 1-phase and 2-phase driving signals.

FIG. 9 is a waveform showing each portion of the apparatus for driving a 2-phase SRM at the time of a normal driving according to the present invention.

As shown, in order to provide a sufficient amount of currents to the SRM at the time of a torque occurrence time point (a mis-aligned time point of the 1-phase inductance profile), the driving sensor is positioned on the shutter so that the driving sensor signals can be risen before the mis-aligned position of the 1-phase inductance profile by a preset angle.

Preferably, the driving sensor signal is risen before the initializing sensor signal of FIG. 5 by 10°˜30°.

The microprocessor generates a 1-phase signal based on rising of the driving sensor signal, and generates a 2-phase signal based on falling of the driving sensor signal, the 2-phase signal having a phase difference of 90° from the 1-phase signal.

Then, the microprocessor generates each phase driving signal by pulse-width modulating the 1-phase signal and the 2-phase signal. That is, the microprocessor generates a 1-phase driving signal by multiplying (AND-operating) the 1-phase signal based on a rising time of the driving sensor signal with a first pulse width modulation signal generated based on a falling time of the driving sensor signal. Also, the microprocessor generates a 2-phase driving signal by multiplying (AND-operating) the 2-phase signal based on a falling time of the driving sensor signal with a second pulse width modulation signal generated based on a rising time of the driving sensor signal.

Differently from each phase signal, the first and second pulse width modulation signals are risen based on the falling time and the rising time of the driving sensor signal, respectively.

For instance, in case of a normal driving of the SRM having 100,000 rpm, the first and second pulse width modulation signals are risen based on the falling time and the rising time of the driving sensor signal, respectively, so as to ensure an operation time of the microprocessor that controls a rotation speed.

The first and second pulse width modulation signals are respectively risen after being delayed by a preset time based on the failing time and the rising time of the driving sensor signal.

The preset time may be a half period of the driving sensor signal, and preferably is a preset rising delay time.

When the SRM is normally driven at a high speed, the 1-phase signal or the 2-phase signal has a short period and thus the microprocessor can not easily control a period of a pulse width modulation signal and a pulse width based on the 1-phase signal or the 2-phase signal. Accordingly, the second pulse width modulation signal is risen by being delayed by a half period (or a rising delay time added to the half period) based on the rising time point of the driving sensor signal. Also, the first pulse width modulation signal is risen by being delayed by a half period (or a rising delay time added to the half period) based on the falling time point of the driving sensor signal.

Preferably, each dwell time of the first and second pulse width modulation signals can be variable.

FIG. 10 is a flowchart showing a method for driving a 2-phase SRM according to the present invention.

As shown, the method for driving a 2-phase SRM according to the present invention comprises generating 1-phase and 2-phase signals by using a driving sensor at the time of a normal driving mode (S61), generating first and second pulse width modulation signals based on the 1-phase or the 2-phase signal (S62), multiplying the 1-phase signal and the 2-phase signal with the first and second pulse width modulation signals thereby generating 1-phase and 2-phase driving signals (S63), and driving the SRM by the 1-phase and 2-phase driving signals (S64).

The second pulse width modulation signal is generated based on a rising time of the 1-phase signal, and the first pulse width modulation signal is generated based on a rising time of the 2-phase signal.

An operation of the apparatus and method for driving a 2-phase SRM according to the present invention will be explained.

At the time of an initial driving, the initializing sensor 71 a detects a position of a rotor thus to generate an initializing sensor signal based on the detected result, thereby applying it to the microprocessor 72.

Then, the microprocessor 72 generates 1-phase and 2-phase signals based on the initializing sensor signal applied from the initializing sensor 71 a.

Then, the oscillator 73 generates first and second pulse width modulation signals based on the 1-phase and 2-phase signals.

Then, the multiplying unit 74 multiplies the 1-phase and 2-phase signals outputted from the microprocessor 72 and the first and second pulse width modulation signals outputted from the oscillator 73 one another, thereby generating 1-phase and 2-phase initializing signals.

The 2-phase SRM is initially driven by the 1-phase and 2-phase initializing signals.

Then, the microprocessor 72 detects an rpm of the 2-phase SRM, and judges whether the detected rpm is more than a preset rpm. If the rpm of the 2-phase SRM is more than the preset rpm, a position of the rotor is detected by the driving sensor 71 b and 1-phase and 2-phase signals are generated based on the detected position of the rotor (S66).

Then, the oscillator 73 generates first and second pulse width modulation signals based on the 1-phase and 2-phase signals, respectively (S67).

The oscillator 73 generates the second pulse width modulation signal based on the 1-phase signal, and generates the first pulse width modulation signal based on the 2-phase signal. That is, the oscillator 73 generates the second pulse width modulation signal based on the rising time of the 1-phase signal, and generates the first pulse width modulation signal based on the rising time of the 2-phase signal.

When the SRM is normally driven at a high speed, the 1-phase signal or the 2-phase signal has a short period and thus the microprocessor can not easily control a period of a pulse width modulation signal and a pulse width based on the 1-phase signal or the 2-phase signal. Accordingly, the oscillator 73 rises the second pulse width modulation signal by delaying by a half period of the driving sensor signal (or a rising delay time added to the half period) based on a rising time point of the driving sensor signal. Also, the oscillator 73 rises the first pulse width modulation signal by delaying by a half period (or a rising delay time added to the half period) of the driving sensor signal based on a falling time point of the driving sensor signal.

Preferably, the oscillator 73 may vary each dwell time of the first and second pulse width modulation signals so as to control a rotation speed of the SRM.

Then, the multiplying unit 74 multiplies the 1-phase and 2-phase signals outputted from the microprocessor 72 and the first and second pulse width modulation signals outputted from the oscillator 73 one another, thereby generating 1-phase and 2-phase driving signals (S68).

The 2-phase SRM is driven by the 1-phase and 2-phase driving signals (S69).

In the present invention, 2-phase of the SRM is initially driven by the initializing sensor at the time of an initial driving, and is normally driven by the driving sensor at the time of a normal driving. Also, the rpm of the SRM can be precisely controlled by delaying each phase signal by a half period and then generating each pulse width modulation signal based on the delayed phase signal.

The apparatus and method for driving a 2-phase SRM of the present invention has the following effects.

An initial driving is performed by the initializing sensor and a normal driving is performed by the driving sensor. Also, a rotation speed of the SRM is controlled by delaying a phase signal by a half period and then generating a pulse width modulation signal based on the period.

Accordingly, a sufficient amount of torque is generated when the SRM is driven at a high speed, and an operation time of the microprocessor is ensured.

It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. An apparatus for driving a 2-phase SRM (switched reluctance motor), comprising: a driving sensor which detects a position of a rotor thus to generate a driving sensor signal based on a result of the detection; a microprocessor which generates a 1-phase signal and a 2-phase signal based on a rising time and a falling time of the driving sensor signal at the time of a normal driving; an oscillator which generates first and second pulse width modulation signals delayed by a preset time; and a multiplying unit which multiplies the 1-phase and 2-phase signals with the first and second pulse width modulation signals, and generates 1-phase and 2-phase driving signals based on a result of the multiplication.
 2. The apparatus of claim 1, wherein the oscillator generates a first pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal.
 3. The apparatus of claim 1, wherein the oscillator generates a second pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal.
 4. The apparatus of claim 1, wherein the oscillator generates the second pulse width modulation signal based on a rising time of the 1-phase signal.
 5. The apparatus of claim 1, wherein the oscillator generates the first pulse width modulation signal based on a rising time of the 2-phase signal.
 6. The apparatus of claim 2, wherein the preset time corresponds to a half period of the driving sensor signal.
 7. A method for driving a 2-phase SRM by using an initializing sensor at the time of an initial driving and a driving sensor at the time of a normal driving, comprising: detecting each position of each phase by the driving sensor thereby generating a driving sensor signal based on the detected result at the time of the normal driving; and driving the 2-phase SRM by delaying by a preset time based on the driving sensor signal generated by the driving sensor.
 8. The method of claim 7, wherein the driving the 2-phase SRM comprises: generating a 1-phase signal based on a rising time and a falling time of the driving sensor signal; generating a first pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal; and generating a 1-phase driving signal based on the 1-phase signal and the first pulse width modulation signal.
 9. The method of claim 7, wherein the driving the 2-phase SRM comprises: generating a 2-phase signal based on a rising time or a falling time of the driving sensor signal; generating a second pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal; and generating a 2-phase driving signal based on the 2-phase signal and the second pulse width modulation signal.
 10. The method of claim 7, wherein the preset time corresponds to a half period of the driving sensor signal.
 11. A method for driving a 2-phase SRM, comprising: detecting each position of each phase by a driving sensor thereby generating a driving sensor signal based on the detected result at the time of a normal driving; generating 1-phase and 2-phase signals based on a rising time or a falling time of the driving sensor signal generated by the driving sensor; generating a first pulse width modulation signal delayed by a preset time based on a falling time of the driving sensor signal, and generating a second pulse width modulation signal delayed by a preset time based on a rising time of the driving sensor signal; and modulating a pulse width of the 1-phase signal based on the first pulse width modulation signal, a modulating a pulse width of the 2-phase signal based on the second pulse width modulation signal, and thereby generating 1-phase and 2-phase driving signals.
 12. The method of claim 11, wherein the preset time corresponds to a half period of the driving sensor signal.
 13. The apparatus of claim 3, wherein the preset time corresponds to a half period of the driving sensor signal. 